As far as I know, there are mainly 2 kinds of Duo Crane. One is unsignatured one made with African Sandalwood frame (that looks like rosewood) and plywood backboard. The other one is signatured one made with Rosewood frame and solid paulownia backboard.
There are different signatures depends on whether you get "Dunhuang" brand or "Yun" brand. It actually dosen't matter, cause I think it this case, the difference is caused mainly by the materials used.

Generally guzhengs are made with "hong mu" frame, which people translate into "red wood", "rosewood", "maghony", etc. They are probably all correct, because there are many species of hong mu in Chinese definetion.

Dunhuangs are good for southern music in general. Zitan sounds pure and clean that's good for southern classics.

If you use a zitan among all the other students using Duo Crane, all you get are jealous eyes from all around. j/k

I like Yuan Sha's VCD tutorials. The blue one is actually not bad. All those VCDs have similar quality. I think Wang Zhongshan's tuotrials are much worse.
Yuan Sha's gray book set is also pretty good for beginner, but the sound/picture quality is not better.

Ah, I wish I have those tutorial VCDs back then when I started learning guzheng. I've acculmuated so many problems that could be corrected right in the beginning. My thumb joint wasn't bending when I pluck, so I was more like pushing the string than plucking the string. That's a common problem for beginners cause we tend to want the pick to be flat with the string. Then it's impossible to build up finger power. Also, my 4 always sound too sharp and 7 sounds flat, cause when I started learning, nobody tells me that you push 4 only half way you push 7, cause 3 and 4 is a half step, 6 and 7 is a whole step. Beginners tend to push 4 and 7 the same way.

My early teachers were all traditional trained that they never paid attention to my problems. It took me years to realize the problems and correct by myself. Yuan Sha is detailed in pointing out all the common problems beginners' tend to make.

ming shan is so hard!!!! Im learning it next though!......... yuan sha's vcd is great! I used it at first without english translation and still seemed to understand her _________________I love guzheng!